From: Al Viro <viro@ZenIV.linux.org.uk>
To: Hannes Eder <hannes@hanneseder.net>
Cc: Christopher Li <sparse@chrisli.org>, linux-sparse@vger.kernel.org
Subject: Re: [PATCH] test-suite: new preprocessor test case
Date: Thu, 19 Mar 2009 18:26:28 +0000 [thread overview]
Message-ID: <20090319182628.GB28946@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20090319175544.13691.42362.stgit@f10box.hanneseder.net>
On Thu, Mar 19, 2009 at 06:56:11PM +0100, Hannes Eder wrote:
> Sparse currently fails on this test.
It doesn't. 6.10.3p11: "If there are sequences of preprocessing tokens
within the list of arguments that would otherwise act as preprocessing
directives, the behavior is undefined."
You are asking for identical nasal demons from two implementations, when
it's not even promised that the same kind will fly on two invocations of
the same implementation...
Seriously, this is undefined behaviour *and* it's extermely hard to come
up with self-consistent semantics for it. Standard doesn't even try and
implementations are doing whatever's more convenient at the moment. Try
to think of it and you'll come up with really ugly corner cases very fast.
What we probably ought to do is a warning when such stuff happens.
next prev parent reply other threads:[~2009-03-19 18:26 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-19 17:56 [PATCH] test-suite: new preprocessor test case Hannes Eder
2009-03-19 18:26 ` Al Viro [this message]
2009-03-19 18:51 ` Hannes Eder
2009-03-19 19:07 ` Nasal demons in preprocessor use (Re: [PATCH] test-suite: new preprocessor test case) Al Viro
2009-03-19 19:27 ` Ingo Molnar
2009-03-19 19:39 ` Al Viro
2009-03-19 20:20 ` Vegard Nossum
2009-03-19 22:07 ` Stephen Rothwell
2009-03-20 18:08 ` Ingo Molnar
2009-03-20 19:04 ` Al Viro
2009-03-20 19:14 ` Al Viro
2009-03-20 23:16 ` Vegard Nossum
2009-03-20 23:44 ` Al Viro
2009-03-21 8:34 ` Johannes Berg
2009-03-27 3:13 ` H. Peter Anvin
2009-03-19 19:24 ` [PATCH] test-suite: new preprocessor test case Derek M Jones
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